1. Based on the sample results in Exercise 10.109, construct and interpret the 95% confidence interval for the population proportion. Is the hypothesized propor- tion (0.25) within the interval? Given the presence or absence of the 0.25 value within the interval, is this con- sistent with the findings of the hypothesis test conducted in Exercise 10.109?
2. In making aluminum castings into alternator housings, an average of 3.5 ounces per casting must be trimmed off and recycled as a raw material.
A new manufacturing procedure has been proposed to reduce the amount of aluminum that must be recycled in this way. For a sample of 35 castings made with the new process, data file XR10111 lists the weights of aluminum trimmed and recycled. Based on the sample data, and using the 0.01 level, has the new procedure significantly reduced the average amount of alumi- num trimmed and recycled? Identify and interpret the p-value for the test.